Biocontrol of WFT and other key pests in commercial greenhouse crops
Capsicum crops frequently suffer heavy losses due to Tomato Spotted Wilt Virus (TSWV) spread by Western Flower Thrips (WFT). These thrips are difficult to control, breed rapidly in warm greenhouse conditions and readily develop resistance to pesticides. As a result pesticide-based programs for controlling WFT are often ineffective. Demonstrated success with a comprehensive bio-control program that can control WFT on commercial farms would provide industry with a viable crop protection alternative. In this project (VG09102) a bio-control program was implemented in a hydroponic capsicum crop with WFT as the primary target. Previous capsicums crops had suffered heavy losses due to high levels of TSWV spread by uncontrollable WFT populations. Secondary pests were also targeted with bio-control agents to prevent them from disrupting the WFT bio-control program. A complete Integrated Pets Management (IPM) strategy was implemented beginning with seedlings raised on farm, a thorough clean-up of the greenhouse, total crop hygiene, routine crop scouting and releasing selected bio-control agents. Several IPM compatible pesticides were identified to support the bio-control program. The backbone of the strategy was Orius armatus, a new and aggressive Australian native predator of WFT. The program encountered major challenges due to the apparent carry over of a WFT population from the previous crop, with adult thrips emerging from residual pupae in the weed mat. This early pest pressure was complicated by very slow establishment of Orius in the crop. Resulting high levels of WFT required pesticide suppression which repeatedly disrupted the overall bio-control program. When Orius became well-established six months later it did an impressive job of cleaning up an „extreme‟ population of WFT. Several other pests (green peach aphids, broad mite, spider mite and caterpillars) were effectively controlled by biological agents and limited use of „soft‟ pesticides. The grower and project team are confident that the problems encountered have provided lessons that will enable success in the next crop and thus recommend support for a subsequent Horticulture Australia Voluntary Contribution program to achieve effective early establishment of Orius as a bio-control agent for WFT. The vegetable industry will be updated on these experiences and outcomes through local training programs and more widely via industry publications. If a second trial is funded, its likely success will support a vigorous extension effort with a strong recommendation for adoption of bio-control of WFT in the greenhouse industry.